The automatic action of an air gun is either fully automatic or semiautomatic. In a firing mechanism for fully automatic action, when a user continues pulling a trigger, bullets are continuously fired until all bullets are exhausted. Since a gun which adopts a fully automatic mechanism has a disadvantage that bullets and gas are consumed at an accelerated pace and the accuracy of fire may deteriorate due to the strong recoil of the gun, in some cases guns which adopt a semiautomatic mechanism are more popular. In a semiautomatic action, the trigger is temporarily disconnected from the firing device (bolt, hammer, sear, etc.).
For example, an air gun as shown in FIG. 11 is known as a conventional open bolt type automatic toy air gun which has a disconnector for the abovementioned disconnection and uses compressed gas. Next, it will be described referring to FIGS. 11 to 13.
FIG. 11 shows the initial state of a conventional open bolt type air gun. The gun body includes a frame 201, a bolt 202, a bolt spring 203, a trigger 204, a trigger spring 205, a sear 206, a sear spring 207, and a sear locking projection 208. As shown in FIG. 12, as the bolt 202 is pulled toward the back of the gun by hand, the bolt moves backward against the biasing force of the bolt spring and locked by a sear lock to stand by for firing. As the trigger is pulled, the sear is released from the bolt and the bolt quickly moves forward by the biasing force of the bolt spring and a hit pin 209 hits a discharge valve 211 in a valve body 210. Consequently, the discharge valve moves forward, which breaks the air tightness in the valve body and fires a bullet by the compressed air which fills the valve body.
Then, the compressed gas in the valve body 210 goes not only toward the muzzle but also toward the rear of the bolt to push the bolt backward, so the bolt begins moving backward against the biasing force of the bolt spring. After the bolt has moved back all the way, the bolt attempts to move forward by the biasing force of the bolt spring, but as shown in FIG. 13, it is locked by the sear 206, which has been returned to its initial state by the sear spring, and stopped while it is held in its cocking position.
At this time, as the user lets his/her finger go from the finger rest of the trigger, the initial state as shown in FIG. 11 is restored by the trigger spring and by pulling the trigger again, a bullet can be fired. Bullets can be fired continuously (semiautomatically) by repeating this cycle.
However, if the gas pressure becomes low and the bolt fails to move backward to the position where it is locked by the sear, the bolt would reciprocate or move forward and backward and bullets would be fired continuously (fully automatically).